1. Field of the Invention
The invention pertains to the field of electrical bonding devices. More particularly, the invention pertains to electrical bonding fasteners having seals against corrosion induced by air and water.
2. Description of Related Art
Bonding devices are commonly used for bonding electrical assemblies, such as frames for solar panel supports or the like. These are often in the form of external tooth lock washers, which have a flat central section and twisted teeth around the perimeter of the washer. The device is placed between the frames, and a fastener such as a bolt or screw passes through the frames and the center of the washer. When the fastener is tightened, the twisted teeth bite into the facing surfaces of the frames to penetrate any surface corrosion or coating and create a good electrical connection.
A problem with the prior art is that air and water are free to pass around the teeth of the washer. Over time the washer, or the surfaces of the frames into which the teeth are biting, can corrode by exposure to air and water. This allows the electrical connection between the frames to degrade.
Wiley Electronics of Saugerties, N.Y., sells a line of bonding devices called WEEB (Washer, Electrical Equipment Bonding) connectors, which are used in assembling and grounding outdoor electrical equipment such as photovoltaic solar panel arrays and the like. The metal teeth of the WEEB clip deform during installation to provide the bonding and some degree of self-sealing, so it is a single-use item and cannot be reused.
U.S. Pat. No. 2,895,524, entitled “Twisted tooth lock washer having anti-skid body section”, is a toothed washer having a resilient o-ring around its inner diameter which is intended to keep the washer from rotating as the bolt is tightened. To the extent that the o-ring provides a seal, it is only on one side and only around the bolt. Water and air are free to infiltrate around the outside of the teeth.
U.S. Pat. Nos. 3,588,787 and 3,626,357, entitled “Electrical Connecting Washer” show a flat washer with o-rings on one side. A circular row of teeth is provided on one side of the washer, roughly midway between the central screw hole and the outer perimeter of the washer, and two o-rings radially inward and outward from the teeth provide a seal, but on one side only. This design does not bond two items, rather is intended to enhance the bond between a screw and the wall to which it is screwed. A wire could be trapped under the screw head, but the electrical connection between wire and screw, or screw and washer, remains open to corrosion.
British published application GB2360076, entitled “A fastener having cutting surfaces and seals” has teeth on the underside of the bolt head, with both inner and outer seals radially inward and outward from the teeth. Similarly, U.S. Pat. No. 3,389,734, entitled “Locking and sealing Screw” patent is a bolt with teeth on the underside of the bolt head and seal area formed from the bolt material radially outside of the teeth. Both of these publications are designed to screw into a threaded hole or fitting on a surface, not to interface with a nut. There is no concern about leakage along the threads, since the inside of a car is dry, and the bolt is not grounding there.
U.S. Pat. No. 6,244,807, entitled “Double seal nut”, is a nut with an outer O-ring to prevent radial leakage between the nut and the surface against which it is tightened and a Teflon inner thread seal to prevent leakage axially along the threads. The nut has no teeth for electrical conduction.